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Area Forecast Discussion (AFD)

Issued by Houston/Galveston, TX (HGX)

                            
000
FXUS64 KHGX 231138
AFDHGX

Area Forecast Discussion
National Weather Service Houston/Galveston TX
538 AM CST Sat Feb 23 2019

.AVIATION...
Visibilites have improved south of the warm front which is draped
south of CLL but north of UTS, but ceilings remain at IFR/LIFR
criteria across all SE TX terminals this morning. A cold front 
will push from NW to SE across the area this morning and into the 
early afternoon, reaching CLL around 12Z and GLS closer to 18Z. 
Showers and isolated thunderstorms will be possible ahead of and 
along the boundary with this frontal passage. Behind the cold 
front, conditions will improve as drier, cooler air ushers in. 
VFR conditions are anticipated by this afternoon, clearing from NW
to SE. Winds will strengthen and be gusty at times (mainly during
the afternoon) with the passing of the front. A secondary shot of
colder and drier air will push into the region during the early 
morning hours Sunday, and as a result winds will shift more 
northerly between 9 and 13 kts.

Hathaway

&&

.PREV DISCUSSION... /ISSUED 348 AM CST Sat Feb 23 2019/ 

DISCUSSION...
A rather complicated weather pattern this morning. At 3 AM, a warm
front extended across SE TX with areas of dense fog north of the
front and along the coast with improved visibility to the south of
the warm front. The front will march slowly north this morning and
most of SE TX will be south of the warm front by 12z. Will be
watching trends but think the Dense Fog Advisory may be canceled
around 12z as visibility improves everywhere but along the
immediate coast where sea fog will remain in place until later
this morning. Low pressure had developed over NE New Mexico with a
weak trough of low pressure or dry line extending south from the
low. The actual cold front still lags behinds in eastern NM. The
low will accelerate to the NE this morning toward southern KS and 
this will allow the cold front to catch up to the dry line/trough 
and rapidly push across the state. The front will trigger a line 
of shra/tsra between 8-11 AM as it crosses SE TX. PW values 
increase to between 1.30 and 1.60 inches but forecast soundings 
show capping in the 850-700 MB layer. The cap is forecast to erode
but not so sure that it will. Low level lapse rates are meager 
but mid level lapse rates look robust. SE TX looks to be in a RRQ
by 18z but by then the front will have already cleared the coast.
It just kind of looks like severe weather parameters are a bit out
of phase and instability parameters look much less impressive 
than yesterday so think it'll be just a broken line of showers and
thunderstorms this morning. SPC has much of SE TX outlooked in 
Marginal Risk for the potential for strong storms. 12z soundings 
will probably give a better idea of cap strength. High PoPs still 
in order as most areas should see some showers ahead of the front 
and shra/tsra with the fropa later this morning.

High temperatures today will be tricky. A very warm start to the
day with temperatures near or exceeding 70 degrees. Skies will
clear rapidly behind the front before cirrus begins to stream
overhead later in the afternoon. West winds will develop behind 
the front will increase and become gusty but the cold air
advection looks weak in the wake of the front. Would not be
surprised if a few locations reached 80 degrees today. The cirrus
and mixing from the winds should limit how warm it gets today.

Generally clear skies are tonight through early Monday. Clouds
begin to return late Monday as onshore winds return and low level
moisture increases. PW values increase to around 1.15 inches and
the moisture profile becomes saturated between the sfc and 800 MB.
Capping is noted above the saturated layer so would expect
just scattered showers beginning late Monday night and probably
persisting into Wednesday. Global models diverge with how to
handle the next cold front. The ECMWF still brings the front
through on Thursday while the GFS and Canadian hold the front back
until Saturday. Am kind of leaning toward the GFS at this time but
basically split the difference for temperatures and PoPS for
Thursday and beyond. 43

MARINE...
A Marine Dense Fog Advisory remains in effect through 10 AM for 
Galveston and Matagorda Bay, and through noon for the nearshore 
waters. A cold front will pass through the Gulf waters by early this 
afternoon which should eliminate fog and improve visibilities as a 
drier airmass ushers in. Showers and isolated thunderstorms will be 
possible with this frontal passage. Behind the front moderate 
west/northwesterly winds will fill in for the remainder of the day. 
Expect to see moderate to strong wind speeds by early Sunday morning 
as a second shot of colder drier air pushes into the region. Winds 
will turn more north/northeasterly behind this secondary boundary 
and SCEC conditions will likely be needed for the near and offshore 
Gulf waters.

High pressure builds into the region by Sunday midday, and wind 
speeds should lower by Sunday evening. Moderate easterly winds will 
prevail by Monday morning, setting up a lengthy fetch across the 
northern Gulf of Mexico. This long easterly fetch looks to continue 
through much of next week, and as a result, tide levels will likely 
be on the rise as early as Monday. Latest model guidance indicates 
forecast tide levels rising to near 2.0 ft above MLLW, but would not 
be surprised if we see tide levels approach closer to 3.0 feet by 
mid week. Therefore, will have to watch for possible run-up issues 
from mid-week on. Otherwise, unsettled weather should return to the 
coastal waters by Tuesday.

Hathaway

&&

.PRELIMINARY POINT TEMPS/POPS...
College Station (CLL)      71  43  64  41  64 /  70   0   0   0   0 
Houston (IAH)              77  48  68  46  65 /  80   0   0   0  10 
Galveston (GLS)            74  54  65  53  63 /  70   0   0   0  20 

&&

.HGX WATCHES/WARNINGS/ADVISORIES...
TX...Dense Fog Advisory until 10 AM CST this morning for the 
     following zones: Austin...Brazoria Islands...Brazos...
     Burleson...Chambers...Coastal Brazoria...Coastal 
     Galveston...Coastal Harris...Coastal Jackson...Coastal 
     Matagorda...Colorado...Fort Bend...Galveston Island and 
     Bolivar Peninsula...Grimes...Houston...Inland Brazoria...
     Inland Galveston...Inland Harris...Inland Jackson...Inland 
     Matagorda...Madison...Matagorda Islands...Montgomery...
     Northern Liberty...Polk...San Jacinto...Southern Liberty...
     Trinity...Walker...Waller...Washington...Wharton.

GM...Dense Fog Advisory until 10 AM CST this morning for the 
     following zones: Galveston Bay...Matagorda Bay.

     Dense Fog Advisory until noon CST today for the following zones: 
     Coastal waters from Freeport to Matagorda Ship Channel TX 
     out 20 NM...Coastal waters from High Island to Freeport TX 
     out 20 NM.

&&

$$

Discussion...43
Aviation/Marine...08